Transgenic construct used to study interactions between insulators and promoters. Consists of 10 UAS sites, an FRT cassette containing a 469bp fragment of the Abd-B Fab-8 insulator (nucleotides 63683 to 64151 in clone DS07696) in the forward orientation, the y coding region, a loxP cassette containing the 469bp Fab-8 fragment in the reverse orientation and the mini-w gene.